Periodontitis is a common complex chronic inflammatory disease initiated by a microbial biofilm and is a significant health burden for the population. This competing renewal investigates variation in human gingival epithelial cells' inflammatory responses that may elucidate human susceptibility to periodontal disease and other chronic inflammatory conditions in general and provide diagnostic and therapeutic tools to treat these complex diseases. TLR deficiencies and altered downstream signaling is now being appreciated in many disease pathologies. Our long-term goal is to unravel human inflammatory dysfunctions that render patients susceptible to periodontal disease. We aim to define the mechanism whereby genetic factors modify the inflammatory response. A major advance in understanding variation comes from our recent observation that there is a hypermethylated TLR2 promoter region in cells with dysfunctional inflammatory responses that exhibited a blunted cytokine response which could hampers anti-inflammatory signaling. Thus inflammatory responses are prolonged and contribute to the inflammatory burden. Our central question in this continuation is Does epigenetic dysregulation creates dysbiosis? Our preliminary data suggest that hyper-methylation of promoter regions in epithelial cells causes a diminished host response by silencing pivotal innate immune genes. The present proposal aims to characterize epithelial cells in vitro by challenging Porphyromonas gingivalis, to test the in vivo model to reverse epigenetic modifications and a clinical study to unravel epigenetic modifications in disease susceptibility. Inhibition of de novo DNA methylation using DNA methyltransferase inhibitors has been regarded as a new therapeutic approach in oncology. Nonetheless, their mechanism of action and specificity of these drugs are not clearly understood. The proposed in vivo model will test the specificity and utility of DNA methyltransferase in restoring the epigenetically silenced TLR related genes. This innovative proposal involves in vitro, in vivo animal and human clinical samples to elucidate disease susceptibility, and introduces DNA methyltransferase inhibitor as a potential therapeutic agent for periodontal disease. Specifically, Aim 1 will determine and engineer the altered methylation pattern of the TLR2 promoter DNA in dysfunctional epithelial cells following P. gingivalis infection. This will utilize DNA methyltransferase inhibitor 5-azacytidine (decitabine) to reverse the methylation of the TLR2 gene promoter to restore the normal TLR2 inflammatory response to P. gingivalis. This aim will test whether TLR2 hypermethylation influences innate immune dysregulation and whether active demethylation restores TLR2 functionality in dysregulated cells. In Aim 2, we will use the oral gavage mouse model to study the ability of P. gingivalis to induce epigenetic changes. The chronic inflammation induced alveolar bone loss will be studied and the consequence of bacterial induced methylation will be investigated. This aim will also test the utility of Decitabine as a therapeutic drug against periodontitis, and in Aim 3, Clinical studies are proposed to investigate epigenetic changes in epithelial cells of individuals with periodontitis. This will address cross-sectionally whether TLR2 promoter hypermethylation is relevant in the natural history of periodontal disease and if it influences a subjects' susceptibility to disease and whether an experimental gingivitis induce epigenetic alteration in the gingiva.